To make the butter, combine all of the ingredients (except the corn and rapeseed oil) with ½ tsp sea salt in a food processor and blitz to a paste. Shape into a little log, wrap in baking parchment and keep in the fridge until needed.
Light your barbecue. When you have glowing grey-white coals, toss the corn with the rapeseed oil and salt and pepper to coat it and then grill it, turning as you go, until golden and starting to char. Immediately slather the butter onto the corn and eat.